Thanks to all who offered their help! I confess to knowing nothing about how logs are used, but it would be a substantial sidetrack from the task at hand to educate myself on this now.
The Excel expression by Peter Meyer is a huge help. It recreates the values reached by Waugh in my spreadsheet and should allow me to produce local dials. I NEVER would have gotten there on my own! =DEGREES(ATAN(TAN(RADIANS(B3))*SIN(RADIANS(latitude)))) - Bryan > On Aug 9, 2022, at 4:08 AM, Peter Mayer <a1000...@adelaide.edu.au> wrote: > > Hi Brian, > > In my experience, using Excel is an excellent way to explore sundial > formulas. > > I wouldn't use logs. Instead use the equation above it: Tan D (hour angle) = > (tan t (time)*sine phi (latitude)). So I think you need > =DEGREES(ATAN(TAN(RADIANS(B3))*SIN(RADIANS(35)))), i.e. at the end, you need > to convert the answer in radians back to degrees. If I use 35 degrees as > latitude, I get 8.73785 degrees = 8 44 which is what Waugh lists on p. 219. > > > best wishes, > > Peter > > On 9/08/2022 15:19:54, Bryan Mumford wrote: >> CAUTION: External email. Only click on links or open attachments from >> trusted senders. >> >> I’m working from Albert Waugh’s book “Sun dials, Their Theory and >> Construction”. On page 45 he presents a method for computing hour lines. I >> lack significant math skills, but I know how to work Excel. I don’t >> understand how he is calculating these values. >> >> He says, for example, that “log tan t” of 7°30’ is 9.11943. >> >> In my simple-minded way I asked Excel to show me log(tan(7)) and got a very >> different value. >> I tried converting 7°30’ to radians and that didn’t get any closer. >> >> How can I calculate "log tan t" or "log sin latitude” with Excel to get the >> values he shows? >> >> I anticipate further problems with the last two columns, but you have to >> start somewhere…. >> >> - Bryan >> >> >> >> --------------------------------------------------- >> https://lists.uni-koeln.de/mailman/listinfo/sundial >> <https://lists.uni-koeln.de/mailman/listinfo/sundial> >> >> > -- > ----------- > Peter Mayer > Department of Politics & International Relations (POLIR) > School of Social Sciences > http://www.arts.adelaide.edu.au/polis/ > <http://www.arts.adelaide.edu.au/polis/> > The University of Adelaide, AUSTRALIA 5005 > Ph : +61 8 8313 5609 > Fax : +61 8 8313 3443 > e-mail: peter.ma...@adelaide.edu.au <mailto:peter.ma...@adelaide.edu.au> > CRICOS Provider Number 00123M > ----------------------------------------------------------- > > This email message is intended only for the addressee(s) > and contains information that may be confidential > and/or copyright. If you are not the intended recipient > please notify the sender by reply email > and immediately delete this email. > Use, disclosure or reproduction of this email by anyone > other than the intended recipient(s) is strictly prohibited. > No representation is made that this email or any attachment > are free of viruses. Virus scanning is recommended and is the > responsibility of the recipient. > -- > https://www.adelaide.edu.au/study/ <https://www.adelaide.edu.au/study/>
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